This invention relates to antennae and more particularly, to omnidirectional microstrip antennae.
A short, vertical rod is the classic omnidirectional antenna. It is omni-directional in a plane perpendicular to its longitudinal axis, vertically polarized in that plane, and may be easily matched with the impedance of ancillary equipment stages. Characteristically, a vertical rod is inefficient, does not remain tuned when placed in different media of radiation, and is particularly sensitive to nearby sensors, oscillators, and transmitters. While two orthogonal vertical loops may be used to provide the proper pattern (i.e., omnidirectional) and desired polarization, interactions between loops detracts from the performance of the antenna. Also, efficiency is low when loops are small compared to the operating wavelength. The noun "ground plane" denotes a conducting or reflecting plane functioning to image a radiating structure.